The packed train, which left Paris on Friday evening with 385 passengers, jumped the track about 20 minutes into a scheduled three-hour journey as it traveled through Bretigny-sur-Orge station. It crashed into the platform and some cars tipped over.
Human error has already been ruled out, according to Transport Minister Frederic Cuvillier, and attention has focused instead on the switching system, which guides trains from one track to another. Investigators found that a piece of metal in one joint in the switch linking two rails had disconnected from its normal position, Pierre Izard, an official with the national rail company, SNCF, told reporters.
"It moved into the center of the switch and in this position it prevented the normal passage of the train's wheels and it may have caused the derailment," he said at a news conference.
Investigators were looking into how this happened since another train had traveled safely through the station about 30 minutes before. In addition, they were trying to figure out why the train's third car was the first to derail. The train was traveling at 137 kph (85 mph), below the limit of 150 kph (93 mph).
Meanwhile, a powerful crane was transferred from northern France to the accident scene to remove damaged cars from the tracks in a difficult operation in which the arm of the crane must reach over buildings to reach the wreckage.
"The SNCF considers itself responsible," the rail company's president, Guilaume Pepy, said. "It is responsible for the lives of its clients."
The train was about 12 miles (20 kilometers) into its 250-mile (400-kilometer) journey to Limoges.
Passengers and officials in train stations throughout France held a minute of silence at noon to commemorate the accident. Hundreds of thousands of people were expected to take trains this weekend for the coast, mountains and to see family. Summer weekends are always busy on France's extensive rail network, but this weekend is typically one of the busiest since the country celebrates Bastille Day on Sunday.
While the death toll has not budged since hours after the crash, Michel Fuzeau, who is the head of local regional government, said that until an overturned train car is lifted, it was impossible to know if there could be more people trapped under it.
"This is only a hypothesis and we hope it's not (the case)," he told reporters.
By Saturday morning, Cuvillier, the transport minister, said 30 people were still hospitalized, including the nine in critical condition. Most of the roughly 200 people injured were either treated at the scene or were hospitalized briefly before being discharged.
The crash was the country's deadliest in years, but Cuvillier said it could have been worse and praised the driver who sent out an alert quickly, preventing a pile up.
Cuvillier acknowledged that there was some criticism that France hasn't invested enough in maintaining infrastructure.
"But for the moment we have no information that allows us to confirm that the dilapidation of the network was the cause of this derailment," he said on French television.
Keira Ichti, who lives in the town where the train crashed, said she was terrified when she found out about the accident because her daughter works at the station. "(It was) total panic. My heart was beating so fast. I had no strength," said the 56-year-old.
She later found her daughter outside the station.
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.